1. Technical Field
This invention generally relates to barriers and security fences, and more specifically relates to barbed tape.
2. Background Art
An early form of metal barrier fence was made of barbed wire. This type of barrier has been in use for more than a century, and is typically rather easy to breach. In addition to lacking the visual intimidation common to more modern barbed tape barriers, barbed wire lacks the strength to resist crushing. To defeat its intended purpose, one need only lay some heavy object over the wire strands, thereby providing a walkway over the barrier.
Barbed tape is designed to overcome these deficiencies. It is more visually intimidating than barbed wire, which features short, unimposing barbs. Barbed tape typically employs razor-sharp barb clusters that can be more than two inches in length. The tape is designed to discourage some breach attempts by its appearance alone. Barbed tape barriers also are typically stronger and harder to crush than barbed wire.
A number of variations of barbed tape already exist. Most variations exhibit the same general features-sharp barbs connected to a central metal strip that is curved into a generally helical shape-and introduce various differences designed to improve upon older designs.
One such design is described in U.S. Pat. No. 2,908,484 granted Oct. 13, 1959 to S. Uhl for “BARBED WIRE SPIRAL.” This barrier includes a metallic strip wrapped completely around a supporting wire made of spring quality steel so that only the barbs extend from the wire (i.e., there is no flange along the wire between barbs). Disadvantages of this barrier include the relatively unimposing appearance of the smaller barbs, and the narrow center strip. Also, the coils are relatively weak in vertical compression.
The barbed tape barrier disclosed in U.S. Pat. No. 4,509,726 granted Apr. 9, 1985 to W. G. Boggs et al. for “BARRIER” consists of a metal strip wrapped part way around a reinforcing wire. The ends of the metal strip, rather than wrapping completely around the wire, extend away from it to form flanges from which the barbs extend. A key feature of this invention is the reduced width of the flange at the barb root intended to open up the tape in those regions so as to increase the penetration capability of the barbs. One deficiency of this barrier is its loss of strength caused by the reduced flange width. Weaker barriers are easier to breach and barriers that collapse easily are less fit for the purpose of preventing the crossing of the barrier.